JP3876129B2 - Transmission electron microscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmission electron microscope, and more particularly to a transmission electron microscope suitable for taking a photograph of a sample that is easily damaged by electron beam irradiation, such as a biological sample.
[0002]
[Prior art]
The present applicant has previously described a minimum electron beam irradiation system that can take a photograph of a sample that is susceptible to electron beam damage, such as a biological sample or an organic sample, with minimal electron beam damage in a transmission electron microscope ( In the following, MDS (referred to as the Minimum Dose System) was proposed. MDS is disclosed in, for example, Japanese Patent Publication No. 59-19408, Japanese Patent Publication No. 61-20108, and “Nippon Denshi News” (Vol.20 No.3 issued on August 20, 1980), which is already publicly known. This will be outlined below with reference to FIG. In FIG. 4, EB is an electron beam, 3 is a focusing lens, 4 is a sample, 5 is an objective lens, 6 is an intermediate lens, 7 is a projection lens, 8 is a fluorescent plate, 10 is a photographing device, 11 is a shutter plate, 20a and 20b. Indicates a deflection coil.
[0003]
The operation of the MDS basically consists of three modes: a visual field search mode, a focusing mode, and a photography mode. In each mode, the focusing lens 3 and the deflection coils 20a and 20b are illustrated according to their purposes. It is automatically controlled by a control circuit that does not.
4A, 4B, and 4C, the point A on the sample 4 is on the optical axis, and the point B is outside the optical axis.
[0004]
An electron beam EB emitted from an electron gun (not shown in FIG. 4) is focused by the focusing lens 3 and irradiated onto the sample 4. The electron beam transmitted through the sample 4 by the electron beam irradiation is magnified by a magnifying lens system including the objective lens 5, the intermediate lens 6, and the projection lens 7, and the magnified elephant of the sample is projected onto the fluorescent plate 8. An enlarged image of the sample 4 is photographed by the photographing device 10 by opening the fluorescent plate 8 by a fluorescent plate driving mechanism (not shown).
The shutter plate 11 is used when taking a picture and is opened and closed by a shutter drive mechanism (not shown).
The deflection coils 20 a and 20 b are two-stage deflection coils placed between the focusing lens 3 and the sample 4. Although this deflection coil may be one stage, it is assumed here that a two-stage deflection coil is used.
[0005]
First, the visual field search mode is operated. In this visual field search mode, the electron beam EB that irradiates the sample 4 is spread by the focusing lens 3, and the ends of the electron beam EB are placed on the optical axis by the deflection coils 20a and 20b. The field of view is searched using the dark electron beam at this end, that is, an electron beam with a small dose of irradiated electrons. That is, by moving the sample 4 from the point A to the point B, it is possible to search for a target visual field under a condition where the electron dose is small. At this time, the excitation current of the focusing lens 3 is controlled to be suitable for the visual field search mode.
[0006]
FIG. 4A shows a ray diagram in the visual field search mode. In the visual field search mode, the focusing lens 3 is strongly excited, and an irradiation electron beam (hereinafter simply referred to as an electron beam) EB is applied to the sample 4. Focusing on the upper side, a wide area of the sample 4 is irradiated. For this reason, the electron current density on the sample 4 becomes low. At this time, the center of the electron beam EB is deflected out of the optical axis by the deflection coils 20a and 20b as shown in the ray diagram of FIG. 4A, and a part of the end of the electron beam EB is on the optical axis. Is deflected to be located at
[0007]
In this state, a desired point is obtained by moving the sample 4 to the left in FIG. 4A by a mechanism (not shown) that horizontally moves the sample while observing the sample image projected on the fluorescent screen 8. A is moved to the center of the fluorescent plate 8, that is, the point of view A is positioned on the optical axis.
[0008]
When the target visual field is searched for by the above visual field searching mode, the visual field searching mode is switched to the focusing mode. At this time, a predetermined constant deflection signal is supplied to the deflection coils 20a and 20b and a current value suitable for focusing is supplied to the focusing lens 3 under the control of the control circuit. Specifically, the excitation of the focusing lens 3 is weakened, and the electron beam EB is substantially focused on the sample 4.
[0009]
FIG. 4B shows a ray diagram at this time. As shown by the solid line in the figure, the electron beam EB is substantially focused on the point B in the sample 4 and the electron beam transmitted through the point B is the objective lens. 5. The enlarged image is formed at the position indicated by P on the fluorescent screen 8 by the intermediate lens 6 and the projection lens 7. At this time, the spot diameter at the point B on the sample 4 is reduced to, for example, 1 μm or less, and the electron flow density becomes high.
[0010]
As described above, in the focusing mode, a preset current is supplied to the focusing lens 3 and the deflection coils 20a and 20b, and the narrowed electron beam EB irradiates the point B outside the optical axis. The point B is imaged on the fluorescent screen 8. Accordingly, in this focusing mode, it is possible to perform focusing accurately by observing the image on the fluorescent screen 8 with a loupe or the like. Further, astigmatism can be corrected if necessary. During this focusing mode, the target field at the point A on the optical axis is not irradiated with the electron beam at all, and the point A is not damaged at all by the electron beam. When the distance from the point A to be photographed in the sample 4, that is, the point A that is the target field of view, to the point B outside the optical axis is short, for example, within 3 μm, the deflection aberration caused by the deflection coils 20a and 20b. , And the off-axis aberration due to the objective lens 5 are confirmed to be sufficiently smaller than the on-axis aberration, and thus focusing and astigmatism correction performed at the point B can be applied to the point A as they are. Is.
[0011]
As described above, when focusing is performed in the focusing mode or astigmatism correction is completed as necessary, the next photography mode is entered. The photography mode can be set by pressing a photography button on the operation panel of the electron microscope. In this photography mode, a current suitable for photography is supplied to the focusing lens 3 by the control circuit, and at the same time, a blanking signal is supplied to the deflection coil 20a. As a result, the electron beam EB is deflected out of the electron beam path as indicated by a broken line in FIG. At this time, the fluorescent plate drive mechanism and the shutter drive mechanism open the fluorescent plate 8 and close the shutter plate 11.
[0012]
Then, after the set time t1 has elapsed, the blanking signal supplied to the deflection coil 20a is stopped. As a result, the center of the electron beam EB is positioned on the optical axis. At this time, excitation suitable for photography of the focusing lens 3 is performed, and the electron beam EB has a large spot diameter and irradiates a wide area of the sample 4 as shown in FIG.
[0013]
After a set time t2 has elapsed since the blanking signal was stopped, the shutter plate 11 is opened, and an enlarged image of the point A on the sample 4 is exposed on the film of the photographing apparatus 10. When the predetermined exposure time t3 has elapsed, the shutter plate 11 is closed again and the fluorescent plate 8 is also closed. The deflection coils 20a and 20b are supplied with a current such that the electron beam EB irradiates a preset point B on the sample 4. Note that the shutter slope 11 is configured to open when the fluorescent plate 8 is closed.
[0014]
As described above, in the photography mode, the fluorescent plate 8 is opened and at the same time the shutter plate 11 is closed to prevent the film from being fogged. Then, the electron beam EB is blanked, and then the current supplied to the focusing lens 3 and the deflection coils 20a and 20b is automatically set to a preset current value, and the electron beam EB is necessary for photographing. The target visual field is irradiated under the condition of the irradiation angle. After this operation, the shutter plate 11 is opened, and the target field of view is photographed.
When the photographing is completed, the system automatically returns to the focusing mode. Therefore, if necessary, a through-focus continuous photograph can be taken without unnecessary electron beam irradiation.
[0015]
FIG. 5 shows a timing chart of a series of operations in the above MDS. In the figure, the horizontal axis indicates time. Further, t1, t2, and t3 are times as described above, and these times can be adjusted by a timer circuit (not shown in FIG. 4). Usually, t1 and t2 are selected to be about 10 seconds and about 0.1 seconds, respectively. As is apparent from FIG. 5, it can be seen that MDS provides the minimum electron beam irradiation in the operation from the field of view search to the photography.
[0016]
By the way, the following problems occur in the MDS described above. As described above, in the focusing mode, the electron beam EB is deflected by a predetermined amount by the deflection coils 20a and 20b. 4B and 4C, the point B on the sample 4 cannot be arbitrarily selected by the operator, and the position where the electron beam EB is deflected by a predetermined amount is the position of the point B. That is, in the MDS described above, the position where the electron beam EB is deflected in the focusing mode is fixed.
[0017]
By the way, the sample 4 is placed on a sample holder provided at the tip of the goniometer. The sample holder has a mesh shape in which a number of metal grids are arranged vertically and horizontally.
Therefore, as shown in FIG. 6, when the point A to be photographed on the sample is in the vicinity of the grid G of the sample holder, the deflection destination of the electron beam EB in the focusing mode is indicated by B in FIG. In some cases, it may come on the grid G. However, focusing cannot be performed on the grid of the sample holder.
[0018]
In view of this, the present applicant has proposed an MDS (hereinafter referred to as an extended MDS for convenience) in which MDS can arbitrarily specify a focus position in the focus mode (hereinafter referred to as an extended MDS). Public technical number 99-4615). Hereinafter, this extended MDS will be schematically described with reference to FIG.
[0019]
FIG. 7 is a diagram showing a schematic configuration example of a transmission electron microscope equipped with an extended MDS function, in which 21 is a TV camera composed of a CCD camera, 22 is a display control device, and 23 is a keyboard or pointing device. An input device 24, a monitor 24 including an appropriate display device such as a CRT or a liquid crystal display device, and an electron microscope main body control section (hereinafter simply referred to as a main body control section) 30. In FIG. 7, the same components as those shown in FIG. In FIG. 7, the focusing lens 3, the deflection coils 20a and 20b, the objective lens 5, the intermediate lens 6, the projection lens 7, the shutter plate 11, and the photographing apparatus 10 shown in FIG. Illustration is omitted for the sake of avoidance.
[0020]
The TV camera 21 is for capturing a magnified image formed on the fluorescent screen 8, and may be an analog camera or a digital camera. Further, the TV camera 21 is arranged so that a point (field center) on the optical axis of the fluorescent screen 8 is located at the center of the captured image. The same applies to this point.
The display control device 22 takes in the video signal from the TV camera 21 and displays it on the monitor 24. Further, when the position on the screen of the monitor 24 is designated by the input device 23, the display control device 22 notifies the main body control unit 30 of information on the designated position as electron beam position control information.
The main body control unit 30 controls operations of the focusing lens 3, the deflection coils 20 a and 20 b, the objective lens 5, the intermediate lens 6, the projection lens 7, and the shutter plate 11 that are not shown in FIG.
In FIG. 7, the TV camera 21, the display control device 22, the input device 23, the monitor 24, and the main body control unit 30 are arranged outside the lens barrel of the electron microscope. An observation window is provided at a position where the lens barrel TV camera 21 is attached. However, the TV camera 21 can also be arranged in the lens barrel.
[0021]
Hereinafter, the operation of the extended MDS will be described.
Also in this extended MDS, first, the visual field search mode is performed. The visual field search mode can be set by pressing a visual field search mode button on an operation panel (not shown) of the main body control unit 30.
[0022]
The operation in the visual field search mode is the same as that of the conventional MDS described above, and the main body control unit 30 controls the lenses 3 to 7 and the deflection coils 20a and 20b to perform the above-described operation. At this time, the display control device 22 displays an enlarged image on the fluorescent screen 8 captured by the TV camera 21 on the monitor 24 and displays a visual field center marker at the center of the screen of the monitor 24. Although this visual field center marker may have any shape, it is assumed to be a “+” shape here.
[0023]
In this state, the operator translates the sample while observing the screen of the monitor 24, and performs an operation of matching the point to be photographed with the position of the visual field center marker. An example of the screen of the monitor 24 at this time is shown in FIG. In FIG. 8A, what is indicated by “+” is a visual field center marker, and the point A to be photographed is made to coincide with the position of the visual field center marker.
[0024]
As described above, when the point A to be photographed is matched with the visual field center marker on the screen of the monitor 24, the visual field search mode is terminated, and then the focusing mode is entered. The setting of the focusing mode can be performed by pressing a button for the focusing mode on the operation panel of the main body control unit 30.
[0025]
In the focusing mode, the operator designates the position of the point B to be focused by the input device 23 while observing the screen of the monitor 24 when the visual field search mode is completed. In this operation, for example, a menu for specifying a focus position is selected by the input device 23, and a desired point on the small 24 screen is designated by the pointing device.
[0026]
For example, when the screen of the monitor 24 when the visual field search mode ends is as shown in FIG. 8A, the position for focusing is on the grid G of the sample holder according to the conventional MDS described above. However, in this extended MDS, the operator can arbitrarily designate the focus position, and therefore, for example, as shown by B in FIG. 8B, the focus position is selected while avoiding the grid G. It is possible.
[0027]
The focusing position is preferably within a predetermined distance from the visual field center marker. This is because if the distance from the center of the field of view becomes long, the deflection aberration caused by the deflection coils 20a and 20b and the off-axis aberration caused by the objective lens 5 may not be ignored with respect to the on-axis aberration.
[0028]
When the focus position is instructed by the input device 23, the display control device 22 takes in the position information of the instructed focus position from the input device 23 and notifies the main body control unit 30 as electron beam position control information. .
[0029]
Based on this electron beam position control information, the main body control unit 30 focuses the electron beam EB at the designated focusing position and performs focusing necessary for irradiation with a predetermined electron current density for focusing. The excitation current of the lens 3 and the excitation current of the deflection coils 20a and 20b are obtained, and the obtained excitation current is supplied to the focusing lens 3 and the deflection coils 20a and 20b. The calculation for obtaining the exciting current of the focusing lens 3 and the exciting currents of the deflection coils 20a and 20b can be performed based on the direction and distance from the center of the visual field of the designated focusing position, and the magnification at this time. .
As a result, an enlarged image of the instructed focusing position is formed on the fluorescent screen 8, and the image is picked up by the TV camera 21 and displayed on the monitor 24. Therefore, the operator observes the image on the screen of the monitor 24. Focus.
[0030]
When focusing is completed, the camera enters the photo shooting mode. The operation in the photo shooting mode is the same as the conventional one, and the description thereof is omitted.
[0031]
As described above, according to the enlarged MDS, the focusing position can be arbitrarily selected within a predetermined distance from the visual field center marker while observing the image on the monitor 24 while avoiding the grid of the sample holder. Can do it.
[0032]
[Problems to be solved by the invention]
By the way, in the electron microscope, there is a case where the sample is observed in a tilted state, but neither the above-described MDS nor the extended MDS considers the case where the sample is tilted. When taking a picture, the above-described MDS or extended MDS cannot be used as it is. That is, when the sample is to be tilted, it is known that the sample is tilted about the tilt axis. The tilt axis is literally the axis when the sample is tilted. And if it is in focus at one point on the tilt axis, it is also known that it is in focus at other points on the tilt axis but not at a point off the tilt axis. Yes.
[0033]
Therefore, consider a case where the extended MDS is used to incline the sample 4 as shown in FIG. 9 and take a picture of the position of the point A on the sample 4. FIG. 9A is a perspective view of the sample 4 viewed from an oblique direction, and FIG. 9B shows a cross-sectional view taken along a line including the points A and B on the sample 4. The point A is assumed to be on the tilt axis J indicated by a broken line in FIG. At this time, if a point B deviating from the tilt axis J is designated as the focus position in the focus mode, the focus is shifted when the photograph is taken after returning to the point A after performing the focus at the point B. Will end up.
[0034]
Therefore, in the case shown in FIG. 9, it is necessary to indicate a point on the tilt axis J as indicated by the black triangle C in FIG. However, in the conventional extended MDS, it is impossible to know where the tilt axis is on the screen of the monitor 24.
[0035]
Of course, it is not impossible to make a note of how much the sample is tilted each time the sample is tilted, and from there it is impossible to calculate where the tilt axis is on the screen of the monitor 24, but it is very troublesome. In addition, since the tilt axis has two axes, X and Y, and the sample can normally be rotated, if the sample is tilted or the sample is rotated several times along these two axes, the monitor 24 is rotated. It is almost impossible to determine the position of each tilt axis on the screen. In addition, even if it is possible to know the position of each tilt axis on the screen of the monitor 24 by appropriate calculation, it takes time, and in the meantime, the sample 4 has an electron. Since the line EB is irradiated, the electron beam damage of the sample proceeds.
[0036]
Therefore, the present invention provides a transmission electron microscope that can easily and accurately set a focusing position on an inclined axis when taking a photograph of a desired position on a sample using an extended MDS. Is intended to provide.
[0037]
[Means for Solving the Problems]
In order to achieve the above object, a transmission electron microscope according to the present invention includes an electron microscope main body control unit that controls each part of the electron microscope main body such as an electromagnetic lens and a deflection coil, and an inclination / rotation for rotating the sample. A rotation mechanism, a TV camera that captures an image formed on the fluorescent screen, a display control device, an input device, and a monitor are provided. The electron microscope main body control unit tilts or rotates the sample by the tilt / rotation mechanism. When the image on the fluorescent screen is rotated by an electromagnetic lens, the tilt direction and its angle, or the tilt direction information is generated based on the rotation direction and its angle and notified to the display control device. Displays a magnified image captured by the TV camera on the monitor and displays a tilt axis pattern on the monitor based on the tilt axis information received from the control unit of the electron microscope main body. When the focus position is instructed by the position, the focus position is set on the tilt axis of the tilt axis pattern that is closest to the indicated position, and information on the focus position is sent to the control unit of the electron microscope. The electronic microscope body control unit controls the respective parts of the electron microscope body so as to focus and irradiate the electron beam at the focusing position based on the information on the focusing position received from the display control device. Features.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the invention will be described with reference to the drawings.
FIG. 1 is a view showing a main part of an embodiment of a transmission electron microscope according to the present invention. In FIG. 1, reference numeral 31 denotes an inclination / rotation mechanism for inclining and rotating a sample. In FIG. 1, the same components as those shown in FIG. 4 and FIG. 7 are denoted by the same reference numerals, and overlapping description is minimized. In FIG. 1, the focusing lens 3, the deflection coils 20a and 20b, the objective lens 5, the intermediate lens 6, the projection lens 7, the shutter plate 11, and the photographing device 10 shown in FIG. Illustration is omitted for the sake of avoidance.
[0039]
This transmission electron microscope is equipped with the above-described extended MDS function.
An inclination / rotation mechanism 31 is connected to the sample 4. The tilt / rotation mechanism 2 is controlled by the main body control unit 30. That is, when the tilt direction and angle are set on the operation panel of the main body control unit 30, the main body control unit 30 provides tilt information including the set tilt direction and angle to the tilt / rotation mechanism 31. Similarly, when the rotation direction and angle are set on the operation panel, the main body control unit 30 provides rotation information including the set rotation direction and angle to the tilt / rotation mechanism 31. Thus, the tilt / rotation mechanism 31 tilts or rotates the sample according to the tilt information or the rotation information. Since the mechanism for tilting and rotating the sample is well known, description thereof is omitted. As a result, the sample 4 is tilted or rotated at the set direction and angle.
[0040]
When the tilt direction and angle are set on the operation panel, the main body control unit 30 determines the position and direction of the tilt axis on the screen of the monitor 24 based on the set tilt direction and angle. It is calculated and it is notified to the display control device 22 as tilt axis information. When the sample is tilted, the position and direction of the tilt axis on the screen of the monitor 24 can be obtained by calculation. That is, the arrangement state of the TV camera 21 is known, and if the observation of the sample is started after returning to a state where there is neither tilt nor rotation, the arrangement state of the TV camera 21 and the inclination of the sample from the start of observation are assumed. Based on the setting state, it is possible to determine in what position and in what direction the tilt axis is on the screen of the monitor 24.
Similarly, when the direction and angle of sample rotation are set on the operation panel, the main body control unit 30 determines the position of the tilt axis on the screen of the monitor 24 based on the set direction and angle of rotation. The direction is determined, and this is notified to the display control device 22 as tilt axis information. The position and the direction of the tilt axis on the screen of the monitor 24 when the sample is rotated can be obtained by calculation as described above.
The main body control unit 30 notifies the display control device 22 of the tilt axis information every time the tilt or rotation of the sample is set.
[0041]
The display control device 22 generates a tilt axis pattern based on the tilt axis information received from the main body control unit 30, and sets the tilt axis pattern to the position indicated by the tilt axis information in the indicated direction. indicate. Since the image from the TV camera 21 is also displayed on the monitor 24 at this time, the image captured by the TV camera 21 and the tilt axis pattern are superimposed on the screen of the monitor 24.
[0042]
An example of such a screen of the monitor 24 is shown in FIG. In FIG. 2A, reference numeral 40 denotes a tilt axis pattern. The enlarged image of the sample is not shown.
A solid straight line displayed at the center of the tilt axis pattern 40 indicates the tilt axis J, and rectangles 41 and 42 having a predetermined width are drawn on both sides of the tilt axis J. These rectangles 41 and 42 are displayed in different colors. The color classification of the rectangles 41 and 424 indicates the inclination direction. For example, if the rectangle 41 indicates the inclination in the positive direction, the rectangle 42 indicates the inclination in the negative direction. Therefore, by observing the tilt axis pattern 40, the operator can easily determine the direction of the positive tilt and the direction of the negative tilt when tilting around the tilt axis J. it can.
Although the above has described the inclination of the sample, the same applies to the rotation of the sample.
[0043]
The display of the tilt axis pattern 40 may be temporarily displayed without being continuously performed. For this purpose, for example, display / non-display of the tilt axis pattern may be selected by the input device 23, or the tilt axis pattern is displayed on the display control device 22 after a certain time has elapsed after the tilt axis pattern is displayed. A function of erasing may be provided.
[0044]
In the description of FIG. 2A, the tilt axis is one axis, but when the sample 4 is tilted with respect to the X and Y axes, the tilt axis pattern display is shown in FIG. Thus, it is desirable to display a plurality of lines. In FIG. 2B, 50 indicates an inclination axis pattern in the X direction, and 60 indicates an inclination axis pattern in the Y direction, for example. Of course, the two inclined axis patterns 50 and 60 are orthogonal to each other.
[0045]
As described above, the tilt axis pattern is superposed and displayed on the monitor 24 with the magnified image of the sample, so that the operator can determine what the current tilt axis is and then tilt it in the positive or negative direction. It is possible to easily determine in a short time whether to incline in the direction, and it is possible to easily predict what will happen when the sample is rotated thereafter.
[0046]
In the above description, the direction of the inclination is displayed in a color-coded rectangle. However, since it is sufficient to display the positive direction and the negative direction, not only the rectangle but also a color-coded arrow or appropriate mark is displayed. You may do it. In addition, what is necessary is just to use the well-known technique which the present applicant proposed in Unexamined-Japanese-Patent No. 2001-57170 about the display of the inclination axis pattern mentioned above.
[0047]
In addition to the function of rotating the sample 4 itself as described above, the electron microscope usually has a function of rotating an enlarged image on the fluorescent screen 8 by adjusting the excitation of the electromagnetic lens. Even when such an image rotation is performed, it is necessary to rotate the tilt axis pattern displayed on the screen of the monitor 24. Therefore, the main body control unit 30 determines which tilt axis is displayed on the screen of the monitor 24 on the basis of the rotation direction and the rotation angle of the image rotation every time an image rotation operation is performed on the operation panel. The display control device 22 is notified as tilt axis information. As a result, the display control device 22 rotates the tilt axis pattern by the direction and angle specified by the tilt axis information.
[0048]
Next, the operation of the operator when taking a picture and the operation at that time will be described. In the following, in order to facilitate understanding, the tilt axis pattern displays only one axis as shown in FIG. 2A, but displays the X and Y tilt axes patterns. The same applies to the case.
[0049]
First, the operator operates the operation panel to set the visual field search mode. At this time, the tilt axis pattern is displayed on the monitor 24.
The basic operation of the operator at this time is as follows. The operator puts the sample 4 in a state where there is no tilt, no rotation, and no translation. At this time, it is assumed that the tilt axis pattern 40 displayed on the screen of the monitor 24 is right side as shown in FIG. In FIG. 3A, a “+” mark with M is a visual field center marker. At this time, it is clear that the visual field center marker M is on the tilt axis J of the tilt axis pattern. In FIG. 3, the enlarged image of the sample is not shown.
[0050]
While observing the screen of the monitor 24 in this state, the operator translates the sample 4 to match the photographing point to be photographed with the position of the visual field center marker M, and then tilts, rotates, or rotates the sample. . At this time, the tilt axis information is notified from the main body control unit 30 to the display control device 22 as described above. At this time, since the sample is not translated, the visual field center marker is at the center of the screen of the monitor 24, and the imaging point coincides with the visual field center marker M.
The excitation of the focusing lens 3 and the deflection coils 20a and 20b at this time is controlled by the main body control unit 30 in the same manner as described above.
[0051]
When the visual field search mode ends in this way, the operator then operates the operation panel to set the focusing mode. Then, the operator designates a focus position using the input device 23. As the focus position, the operator designates a photographing point, that is, a point on the tilt axis J other than the visual field center marker M.
[0052]
Although this focusing position is instructed using the pointing device of the input device 23, the point on the tilt axis J cannot always be instructed accurately. Therefore, the display control device 22 takes in the point on the tilt axis J that is closest to the point designated by the pointing device as the focus position. A so-called rounding process is performed.
[0053]
For example, if the tilt axis pattern 40 is as shown in FIG. 3B when the visual field search mode ends, and the operator points to the point B in the figure that is slightly off the tilt axis J, the display control device 22 The point B ′ on the tilt axis J closest to the point B is set as the focusing position. It is obvious that the point B ′ on the tilt axis J closest to the point B is the intersection with the perpendicular line extending from the point B to the tilt axis J.
[0054]
Although the grid of the sample holder is not shown in FIG. 3B, as described above, the grid is avoided to indicate the focusing position. In addition, as described above, the focus position is instructed to be within a predetermined distance from the visual field center marker M.
The excitation of the focusing lens 3 and the deflection coils 20a and 20b at this time is also controlled by the main body control unit 30 in the same manner as described above.
[0055]
When the focus position is instructed by the input device 23, the display control device 22 takes in the position information of the focus position from the input device 23 and notifies the main body control unit 30 as the electron beam position control information.
[0056]
Based on this electron beam position control information, the main body control unit 30 focuses the electron beam EB at the designated focusing position and performs focusing necessary for irradiation with a predetermined electron current density for focusing. The excitation current of the lens 3 and the excitation current of the deflection coils 20a and 20b are obtained, and the obtained excitation current is supplied to the focusing lens 3 and the deflection coils 20a and 20b. As a result, an enlarged image of the instructed focusing position is formed on the fluorescent screen 8, and the image is picked up by the TV camera 21 and displayed on the monitor 24. Therefore, the operator observes the image on the screen of the monitor 24. Focus.
When focusing is completed, the camera enters the photo shooting mode. The operation in the photo shooting mode is the same as the conventional one, and the description thereof is omitted.
[0057]
As described above, according to the transmission electron microscope, in addition to the effect of the extended MDS described above, the focusing position can be easily indicated on the tilt axis J in a short time. Line damage can be minimized.
[0058]
The basic operation and operation at the time of taking a picture have been described above. However, since the shooting point and the focusing position may be set on the tilt axis J of the tilt axis pattern, the shooting point is not necessarily the field of view. It is not necessary to match the center marker M. Further, a plurality of shooting points can be set on the tilt axis J, and the shooting order of the shooting points in that case may be set appropriately by the operator. In the display control device 22 or the main body control unit 30, For example, the shooting order of the shooting points may be automatically determined in order from the left of the tilt axis J or randomly using a random number. In this case, after the shooting of one shooting point is completed, the electron beam EB may be deflected to the next shooting point.
[Brief description of the drawings]
FIG. 1 is a diagram showing a main part of an embodiment of a transmission electron microscope according to the present invention.
FIG. 2 is a diagram illustrating an example of display of a tilt axis pattern.
3 is a diagram showing an example of a screen displayed on a monitor 24 in a visual field search mode in the transmission electron microscope shown in FIG. 1. FIG.
FIG. 4 is a diagram for explaining the operation of MDS;
FIG. 5 is a timing chart of a series of operations in MDS.
FIG. 6 is a diagram for explaining a problem of MDS.
FIG. 7 is a diagram illustrating a schematic configuration example of a transmission electron microscope equipped with an extended MDS function.
FIG. 8 is a diagram for explaining a function of extended MDS;
FIG. 9 is a diagram for explaining a problem to be solved by the present invention.
[Explanation of symbols]
EB ... electron beam, 3 ... focusing lens, 4 ... sample, 5 ... objective lens, 6 ... intermediate lens, 7 ... projection lens, 8 ... fluorescent plate, 10 ... photographing device, 11 ... shutter plate, 20a, 20b ... deflection coil, DESCRIPTION OF SYMBOLS 21 ... TV camera, 22 ... Display control apparatus, 23 ... Input device, 24 ... Monitor, 30 ... Electron microscope main body control part, 31 ... Inclination and rotation mechanism.

Claims (1)

An electron microscope main body control unit for controlling each part of the electron microscope main body such as an electromagnetic lens and a deflection coil;
A tilting / rotating mechanism for tilting or rotating the sample;
A TV camera that captures an image formed on the fluorescent screen;
A display control device;
An input device;
With a monitor,
When the specimen is tilted or rotated by the tilt / rotation mechanism, or when the image on the fluorescent screen is rotated by the electromagnetic lens, the electron microscope main body control unit is based on the tilt direction and its angle, or the rotation direction and its angle. To generate tilt axis information and notify the display controller,
The display control device displays an enlarged image captured by the TV camera on the monitor, and displays a tilt axis pattern on the monitor based on the tilt axis information received from the control unit of the electron microscope, and the focus position is determined by the input device. If instructed, set the focus position on the tilt axis of the tilt axis pattern that is closest to the indicated position, and notify the electron microscope main body control unit of information on the focus position,
The electron microscope main body control unit controls each part of the electron microscope main body so as to focus and irradiate the electron beam on the focus position based on the information on the focus position received from the display control device. Transmission electron microscope.

Images